Minimally invasive procedures have been implemented in a variety of medical settings, e.g., for vascular interventions, such as angioplasty, stenting, embolic protection, electrical heart stimulation, heart mapping and visualization, and the like. These procedures generally rely on accurately navigating and placing instruments within a patient's vasculature.
During such procedures, a target vessel may be accessed using a guidewire advanced through the intervening vasculature into the target vessel, thereby providing a “railway” to the vessel. One or more instruments, e.g., catheters, sheaths, and the like, may be advanced over the guidewire or “rail” into the vessel. Thus, a diagnostic and/or therapeutic procedure may be performed by advancing one or more instruments over this railway.
There are many risks involved with advancing instruments over a guidewire. For example, a catheter or other instrument may skive or otherwise damage a wall of a vessel, particularly as the instrument passes through narrow passages or tortuous anatomy involving sharp bends. Such instruments also risk dislodging embolic material or even perforating the vessel wall.
In addition, it is often desirable to access very small vessels deep within the body, e.g., within a patient's heart, for example, to place a ventricular pacing lead within a coronary vein. However, the instrument(s), e.g., guide sheath, lead, etc., may have a relatively large cross-section and/or may have a relatively blunt distal tip, making it difficult to advance such instruments as deeply as desired into such small vessels.
Further, it may be desirable to deliver diagnostic and/or therapeutic agents into cardiac tissue. For example, stem cells are a potentially therapeutic agent, which may be delivered to tissue, e.g., cardiac tissue to facilitate regeneration of myocardial cells in dead or damaged tissue, resulting from an infarction or other cardiac event. However, it may be difficult to deliver such agents into cardiac tissue, because of the difficulty in accessing such regions, particularly adjacent relatively small vessels. In addition, delivering agents into a vessel or other body lumen may result in migration and/or dilution of the agents, e.g., due to normal blood flow, which may impair efficacy of the agents.
Accordingly, apparatus and methods for delivering agents into cardiac or other tissue surrounding blood vessels or other body lumens would be useful.